This invention relates to heteroaryl fused aminoalkylimidazole derivatives which when appropriately substituted selectively bind to GABAA receptors. This invention also relates to pharmaceutical compositions comprising such compounds and to the use of such compounds in enhancing alertness and treating anxiety, overdoses of benzodiazepine-type drugs, Down Syndrome, depression, sleep, seizure and cognitive disorders both in human as well as domestic pets and livestock.
The compounds of this invention are also useful as probes for the localization of cell surface receptors.
The GABAA receptor superfamily represents one of the classes of receptors through which the major inhibitory neurotransmitter, xcex3-aminobutyric acid, or GABA, acts. Widely, although unequally, distributed through the mammalian brain, GABA mediates many of its actions through a complex of proteins called the GABAA receptor, which causes alteration in chloride conductance and membrane polarization.
A number of cDNAs for GABAA receptor subunits have been characterized. To date at least 6xcex1, 3xcex2, 3xcex3, 1xcex5, 1xcex4 and 2xcfx81 subunits have been identified. It is generally accepted that native GABAA receptors are typically composed of 2xcex1, 2xcex2, and 1xcex3 subunits (Pritchett and Seeburg Science 1989; 245:1389-1392 and Knight et. al., Recept. Channels 1998; 6:1-18). Evidence such as message distribution, genome localization and biochemical study results suggest that the major naturally occurring receptor combinations are xcex11xcex22xcex32, xcex12xcex23xcex32, xcex13xcex23xcex32, and xcex15xcex23xcex32 (Mohler et. al. Neuroch. Res. 1995; 20(5): 631-636).
Benzodiazepines exert their pharmacological actions by interacting with the benzodiazepine binding sites associated with the GABAA receptor. In addition to the benzodiazepine site, the GABAA receptor contains sites of interaction for several other classes of drugs. These include a steroid binding site, a picrotoxin site, and the barbiturate site. The benzodiazepine site of the GABAA receptor is a distinct site on the receptor complex that does not overlap with the site of interaction for GABA or for other classes of drugs that bind to the receptor (see, e.g., Cooper, et al., The Biochemical Basis of Neuropharmacology, 6th ed., 1991, pp. 145-148, Oxford University Press, New York). Early electrophysiological studies indicated that a major action of the benzodiazepines was enhancement of GABAergic inhibition. Compounds that selectively bind to the benzodiazepine site and enhance the ability of GABA to open GABAA receptor channels are agonists of GABA receptors. Other compounds that interact with the same site but negatively modulate the action of GABA are called inverse agonists. Compounds belonging to a third class bind selectively to the benzodiazepine site and yet have little or no effect on GABA activity, but can block the action of GABAA receptor agonists or inverse agonists that act at this site. These compounds are referred to as antagonists.
The important allosteric modulatory effects of drugs acting at the benzodiazepine site were recognized early and the distribution of activities at different receptor subtypes has been an area of intense pharmacological discovery. Agonists that act at the benzodiazepine site are known to exhibit anxiolytic, sedative, and hypnotic effects, while compounds that act as inverse agonists at this site elicit anxiogenic, cognition enhancing, and proconvulsant effects. While benzodiazepines have a long history of pharmaceutical use as anxiolytics, these compounds often exhibit a number of unwanted side effects. These may include cognitive impairment, sedation, ataxia, potentiation of ethanol effects, and a tendency for tolerance and drug dependence.
GABAA selective ligands may also act to potentiate the effects of certain other CNS active compounds. For example, there is evidence that selective serotonin reuptake inhibitors (SSRIs) may show greater antidepressant activity when when used in combination with GABAA selective ligands than when used alone.
This invention relates to heteroaryl fused aminoalkyl-derivatives. Preferred compounds of the invention that bind with high affinity to the benzodiazepine site of the GABAA receptor, including human GABAA receptors. Preferred compounds of the invention also bind with high selectivity to the benzodiazepine site of the GABAA receptor.
The invention provides novel compounds of Formula I (shown below), and pharmaceutical compositions comprising compounds of Formula I.
The invention further comprises methods of treating patients suffering from certain CNS disorders with an effective amount of a compound of the invention. The patient may be a human or other mammal. Treatment of humans, domesticated companion animals (pets) or livestock animals suffering such conditions with an effective amount of a compound of the invention is contemplated by the invention.
In a separate aspect, the invention provides a method of potentiating the actions of other CNS active compounds. This method comprises administering an effective amount of a compound of the invention with another CNS active compound.
Additionally this invention relates to the use of the compounds of the invention as probes for the localization of GABAA receptors in tissue sections. Such probes are useful for in vitro studies, such as binding assays and autoradiography of tissue sections and for in vivo techniques such as PET and SPECT scans.
Packaged pharmaceutical compositions including instructions for use of the composition are also included.
In a separate aspect, the invention provides a method of potentiating the actions of other CNS active compounds. This method comprises administering an effective amount of a compound of the invention with another CNS active compound.
The invention furthermore provides methods of using compounds of this invention as positive controls in assays for receptor activity and using appropriately labeled compounds of the invention as probes for the localization of receptors, particularly GABAA receptors, in tissue sections. Such probes are useful for in vitro studies, such as binding assays and autoradiography of tissue sections and for in vivo techniques such as PET and SPECT scans.
Accordingly, a broad embodiment of the invention is directed to compounds of Formula I: 
or the pharmaceutically acceptable non-toxic salts thereof wherein:
W represents 
xe2x80x83where Z is O, or S:
R1 represents phenyl, C1-C6 alkyl, cyclopentyl, cyclohexyl, benzyl, 3-fluorobenzyl, or cyclopropylmethyl;
R2 represents hydroxyl, C1-C6 alkyl or C1-C6 alkoxy, either of which could be substituted with amino or mono or di(C1-C6) alkylamino, additionally the alkyl portion can form a 5,6,7 member ring; or O(CH2)nCO2R8 where n=1,2,3,4, NR8COR9, COR8, CONR8R9 or CO2R8 where R8 and R9 are the same or different and represent hydrogen or C1-C6 alkyl, additionally R8 and R9 can be a 5,6,7 member heterocyclic ring;
R3 represents C1-C6 alkyl, allyl, cyclopropylmethyl, cyclopentyl; or benzyl optionally mono-, di-, or trisubstituted independently with halogen, nitro, trifluoromethyl, trifluoromethoxy, cyano, hydroxyl, C1-C6 alkyl or C1-C6 alkoxy, either of which could be substituted with amino or mono or di(C1-C6) alkylamino, additionally the alkyl portion can form a 5,6,7 member ring; or O(CH2)nCO2R8 where n=1,2,3,4, NR8COR9, COR8, CONR8R9 or CO2R8 where R8 and R9 are the same or different and represent hydrogen or C1-C6 alkyl, additionally R8 and R9 can be a 5,6,7 member heterocyclic ring, additional substitution on the benzyl ring can be directly bound or O(CH2)n (where n=1,2,3,4) linked SO2R8, NHSO2R8, SO2NHR8, SO2NHCOR8, CONHSO2R8, as well as tetrazole, triazole, imidazole, thiazole, oxazole, thiophene, and pyridyl;
R4, R5 and R6 are the same or different and represent hydrogen, C1-C6 alkyl or C1-C6 alkoxy, either of which could be substituted with amino or mono or di(C1-C6) alkylamino, additionally the alkyl portion can form a 5,6,7 member ring, C1-C6 alkylthiol, or halogen, or O(CH2)nCO2R8 where n=1,2,3,4, NR8COR9, COR8, CONR8R9 or CO2R8 where R8 and R9 are the same or different and represent hydrogen or straight or branched chain lower alkyl having 1-6 carbon atoms, additionally R8 and R9 can be a 5,6,7 member heterocyclic ring, additionally R4 and R5 can form a 1,3-dioxolene ring;
X represents a bond, CH2, or CHCH;
A,B,C,D are the same or different and represent CH or N with the proviso that not more than two of A,B,C, or D represent N.
Preferred compounds of the invention are highly selective agonists, antagonists or inverse agonists for GABAA brain receptors or prodrugs of agonists, antagonists or inverse agonists for GABAa brain receptors, the benzodiazepine receptor. These compounds are useful in the diagnosis and treatment of anxiety, Down Syndrome, depression, sleep and seizure disorders, cognitive disorders overdose with benzodiazepine drugs, and enhancement of alertness, both in human and non-human animals and domestic pets, especially dogs and cats and farm animals such as sheep, swine and cattle.
Thus, the invention also provides methods and compositions for treating and diagnosing anxiety, Down Syndrome, depression, sleep, cognitive and seizure disorders, and overdose with benzodiazepine drugs.
In another aspect, the invention encompasses compounds that are intermediates in the synthesis of the compounds of Formula I.
The compounds encompassed by the instant invention are represented by the general formula I: 
or pharmaceutically acceptable non-toxic salts thereof wherein:
W represents 
xe2x80x83where
Z is O, or S;
R1 represents phenyl, C1-C6 alkyl, cyclopentyl, cyclohexyl, benzyl, 3-fluorobenzyl, or cyclopropylmethyl;
R2 represents hydroxyl;
C1-C6 alkyl or C1-C6 alkoxy, each of which are optionally substituted with amino, mono or di(C1-C6) alkylamino, a C5-C7 heterocycloalkyl group where the heteroatom is nitrogen and the nitrogen is attached to the parent alkyl portion;
O(CH2)nCO2R8 where n=1,2,3,4, NR8COR9, COR8, CONR8R9 or CO2R8 where R8 and R9 are the same or different and represent hydrogen or C1-C6 alkyl; or
NR8R9 forms a 5-, 6-, or 7-membered heterocyclic ring;
R3 represents
C1-C6 alkyl, allyl, cyclopropylmethyl, cyclopentyl; or
benzyl optionally mono-, di-, or trisubstituted independently with
halogen, nitro, trifluoromethyl, trifluoromethoxy, cyano, or hydroxy;
C1-C6 alkyl or C1-C6 alkoxy, each of which is optionally substituted with amino, mono or di(C1-C6) alkylamino, a C5-C7 heterocycloalkyl group where the heteroatom is nitrogen and the nitrogen is attached to the parent alkyl portion;
O(CH2)nCO2R8 where n=1,2,3,4, NR8COR9, COR8, CONR8R9 or CO2R8 where R8 and R9 are the same or different and represent hydrogen or C1-C6 alkyl;
NR8R9 forms a 5-, 6-, 7-membered heterocyclic ring;
SO2R8, NHSO2R8, SO2NHR8, SO2NHCOR8, CONHSO2R8 where R8 is defined as above;
O(CH2)nxe2x80x94G where n=1,2,3,4 and G is SO2R8, NHSO2R8, SO2NHR8, SO2NHCOR8, or CONHSO2R8, where R8 is as defined above; or
tetrazole, triazole, imidazole, thiazole, oxazole, thiophene, or pyridyl;
R4, R5 and R6 are the same or different and represent hydrogen; or
C1-C6 alkyl or C1-C6 alkoxy, each of which is optionally substituted with amino, mono or di(C1-C6) alkylamino, a C5-C7 heterocycloalkyl group where the heteroatom is nitrogen and the nitrogen is attached to the parent alkyl portion, C1-C6 alkylthiol, or halogen;
O(CH2)nCO2R8 where n=1,2,3,4, NR8COR9, COR8, CONR8R9 or CO2R8 where R8 and R9 are the same or different and represent hydrogen or C1-C6 alkyl;
NR8R9 forms a 5-, 6-, or 7-membered heterocyclic ring; or
R4 and R5 can form a 1,3-dioxolene ring;
X represents a bond, CH2, or CHCH; and
A, B, C, and D are the same or different and represent CH or N with the proviso that not more than two of A,B,C, or D represent N.
In formula I, R2 may also represent
hydrogen or
a group of the formula 
xe2x80x83where
Rn and Rk independently represent C1-C6 alkyl, C2-C6 alkenyl, C1-C6 cycloalkyl(C1-C6)alkyl, benzoyl where the phenyl portion is optionally substituted with halgoen, C1-C6 alkyl, or C1-C6 alkoxy;
a group of the formula IV-a 
xe2x80x83where p, s, and t independently represent 1 or 2;
J is CH, N, O, S, or a carbon atom substituted with C1-C6 alkyl; or
NRkRn represents 
xe2x80x83where s, t, and J are as defined above.
Preferred compounds of the invention are represented by Formula II. 
R1 represents phenyl, C1-C6 alkyl, cyclopentyl, cyclohexyl, benzyl, 3-fluorobenzyl, or cyclopropylmethyl;
R2 represents hydroxyl, C1-C6 alkyl or C1-C6 alkoxy, either of which could be substituted with amino or mono or di(C1-C6) alkylamino, additionally the alkyl portion can form a 5,6,7 member ring; or O(CH2)nCO2R8 where n=1,2,3,4, NR8COR9, COR8, CONR8R9 or CO2R8 where R8 and R9 are the same or different and represent hydrogen or C1-C6 alkyl, additionally R8 and R9 can be a 5,6,7 member heterocyclic ring;
R3 represents C1-C6 alkyl, allyl, cyclopropylmethyl, cyclopentyl; or benzyl optionally mono-, di-, or trisubstituted independently with halogen, nitro, trifluoromethyl, trifluoromethoxy, cyano, hydroxyl, C1-C6 alkyl or C1-C6 alkoxy, either of which could be substituted with amino or mono or di(C1-C6) alkylamino, additionally the alkyl portion can form a 5,6,7 member ring; or O(CH2)nCO2R8 where n=1,2,3,4, NR8COR9, COR8, CONR8R9 or CO2R8 where R8 and R9 are the same or different and represent hydrogen or C1-C6 alkyl, additionally R8 and R9 can be a 5,6,7 member heterocyclic ring, additional substitution on the benzyl ring can be directly bound or O(CH2)n (where n=1,2,3,4) linked SO2R8, NHSO2R8, SO2NHR8, SO2NHCOR8, CONHSO2R8, as well as tetrazole, triazole, imidazole, thiazole, oxazole, thiophene, and pyridyl;
R4, R5 and R6 are the same or different and represent hydrogen, C1-C6 alkyl or C1-C6 alkoxy, either of which could be substituted with amino or mono or di(C1-C6) alkylamino, additionally the alkyl portion can form a 5,6,7 member ring, C1-C6 alkylthiol, or halogen, or O(CH2)nCO2R8 where n=1,2,3,4, NR8COR9, COR8, CONR8R9 or CO2R8 where R8 and R9 are the same or different and represent hydrogen or straight or branched chain lower alkyl having 1-6 carbon atoms, additionally R8 and R9 can be a 5,6,7 member heterocyclic ring, additionally R4 and R5 can form a 1,3-dioxolene ring;
X represents a bond, CH2, CHCH;
A,B,C,D are the same or different and represent CH or N with the proviso that not more than two of A,B,C, or D represent N.
Other preferred compounds of the invention are represented by Formula III. 
where Z is O, or S;
R1 represents phenyl, C1-C6 alkyl, cyclopentyl, cyclohexyl, benzyl, 3-fluorobenzyl, or cyclopropylmethyl;
R2 represents hydroxyl, C1-C6 alkyl or C1-C6 alkoxy, either of which could be substituted with amino or mono or di(C1-C6) alkylamino, additionally the alkyl portion can form a 5,6,7 member ring; or O(CH2)nCO2R8 where n=1,2,3,4, NR8COR9, COR8, CONR8R9 or CO2R8 where R8 and R9 are the same or different and represent hydrogen or C1-C6 alkyl, additionally R8 and R9 can be a 5,6,7 member heterocyclic ring;
R3 represents C1-C6 alkyl, allyl, cyclopropylmethyl, cyclopentyl; or benzyl optionally mono-, di-, or trisubstituted independently with halogen, nitro, trifluoromethyl, trifluoromethoxy, cyano, hydroxyl, C1-C6 alkyl or C1-C6 alkoxy, either of which could be substituted with amino or mono or di(C1-C6) alkylamino, additionally the alkyl portion can form a 5,6,7 member ring; or O(CH2)nCO2R8 where n=1,2,3,4, NR8COR9, COR8, CONR8R9 or CO2R8 where R8 and R9 are the same or different and represent hydrogen or C1-C6 alkyl, additionally R8 and R9 can be a 5,6,7 member heterocyclic ring, additional substitution on the benzyl ring can be directly bound or O(CH2)n (where n=1,2,3,4) linked SO2R8, NHSO2R8, SO2NHR8, SO2NHCOR8, CONHSO2R8, as well as tetrazole, triazole, imidazole, thiazole, oxazole, thiophene, and pyridyl;
R4, R5 and R6 are the same or different and represent hydrogen, C1-C6 alkyl or C1-C6 alkoxy, either of which could be substituted with amino or mono or di(C1-C6) alkylamino, additionally the alkyl portion can form a 5,6,7 member ring, C1-C6 alkylthiol, or halogen, or O(CH2)nCO2R8 where n=1,2,3,4, NR8COR9, COR8, CONR8R9 or CO2R8 where R8 and R9 are the same or different and represent hydrogen or straight or branched chain lower alkyl having 1-6 carbon atoms, additionally R8 and R9 can be a 5,6,7 member heterocyclic ring, additionally R4 and R5 can form a 1,3-dioxolene ring;
X represents a bond, CH2, CHCH;
A,B,C,D are the same or different and represent CH or N with the proviso that not more than two of A,B,C, or D represent N.
More preferred compounds of Formula I are represented by Formula IV 
where
R4, R5, and R6 are as defined above for Formula I;
R1 and R3 are independently C1-C6 alkyl;
and Ra and Rb are independently
hydrogen or
a group of the formula 
xe2x80x83where
Rn and Rk independently represent C1-C6 alkyl, C2-C6 alkenyl, C1-C6 cycloalkyl(C1-C6)alkyl, benzoyl where the phenyl portion is optionally substituted with halgoen, C1-C6 alkyl, or C1-C6 alkoxy;
a group of the formula IV-a 
xe2x80x83where p, s, and t independently represent 1 or 2;
J is CH, N, O, or a carbon atom substituted with C1-C6 alkyl; or
NRkRn represents 
xe2x80x83where s, t, and J are as defined above.
Preferred compounds of Formula IV include those where R1 is propyl and R3 is C3-C5 alkyl, preferably isobutyl. More preferred compounds of IV are those where Rb is hydrogen and Ra is xe2x80x94NHRn where Rn is defined as above or xe2x80x94NRkRn where both Rn and Rk are allyl or C1-C6 alkyl.
Preferred xe2x80x94NRkRn groups include diallylamino, dimethylamino, diethylamino, and N-ethyl-N-cyclopropylmethylamino.
Preferred NHRn groups include those where Rn is allyl, C1-C6 alkyl, or a group of IV-a. Preferred IV-a groups include pyrrolidinyl, morpholinyl and piperidinyl.
Particularly preferred compounds of IV are those where R1 is propyl, R3 is isobutyl, Rb is hydrogen, and Ra is
In certain situations, the compounds of Formula I may contain one or more asymmetric carbon atoms, so that the compounds can exist in different stereoisomeric forms. These compounds can be, for example, racemates or optically active forms. In these situations, the single enantiomers, i.e., optically active forms, can be obtained by asymmetric synthesis or by resolution of the racemates. Resolution of the racemates can be accomplished, for example, by conventional methods such as crystallization in the presence of a resolving agent, or chromatography, using, for example a chiral HPLC column.
Representative compounds of the present invention, which are encompassed by Formula I, include, but are not limited to the compounds described in the Examples and their pharmaceutically acceptable acid addition salts. In addition, if the compound of the invention is obtained as an acid addition salt, the free base can be obtained by basifying a solution of the acid salt. Conversely, if the product is a free base, an addition salt, particularly a pharmaceutically acceptable addition salt, may be produced by dissolving the free base in a suitable organic solvent and treating the solution with an acid, in accordance with conventional procedures for preparing acid addition salts from base compounds.
Non-toxic pharmaceutical salts include salts of acids such as hydrochloric, phosphoric, hydrobromic, sulfuric, sulfinic, formic, toluenesulfonic, methanesulfonic, nitric, benzoic, citric, tartaric, maleic, hydroiodic, alkanoic such as acetic, HOOCxe2x80x94(CH2)nxe2x80x94COOH where n is 0-4, and the like. Those skilled in the art will recognize a wide variety of non-toxic pharmaceutically acceptable addition salts.
The present invention also encompasses the acylated prodrugs of the compounds of Formula I. Those skilled in the art will recognize various synthetic methodologies which may be employed to prepare non-toxic pharmaceutically acceptable addition salts and acylated prodrugs of the compounds encompassed by Formula I.
By xe2x80x9calkylxe2x80x9d or xe2x80x9clower alkylxe2x80x9d in the present invention is meant C1-C6 alkyl, i.e., straight or branched chain alkyl groups having 1-6 carbon atoms, such as, for example, methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, 2-pentyl, isopentyl, neopentyl, hexyl, 2-hexyl, 3-hexyl, and 3-methylpentyl. Preferred C1-C6 alkyl groups are methyl, ethyl, propyl, butyl, cyclopropyl or cyclopropylmethyl.
By xe2x80x9calkoxyxe2x80x9d or xe2x80x9clower alkoxyxe2x80x9d in the present invention is meant C1-C6 alkoxy, i.e., straight or branched chain alkoxy groups having 1-6 carbon atoms, such as, for example, methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, pentoxy, 2-pentyl, isopentoxy, neopentoxy, hexoxy, 2-hexoxy, 3-hexoxy, and 3-methylpentoxy.
By (hetero) cyclic ring is meant a ring that is either aliphatic or aromatic and optionally contains at least one hetero atom. Hetero atoms include nitrogen, sulfur, and oxygen. Examples of such (hetero) cyclic rings are cyclohexyl, cyclopenyl, cyclohexyl, piperidinyl, piperazinyl, pyrrolidinyl, morpholinyl, etc.
By heteroaryl (aromatic heterocycle) in the present invention is meant one or more aromatic ring systems of 5-, 6-, or 7-membered rings containing at least one and up to four hetero atoms selected from nitrogen, oxygen, or sulfur. Such heteroaryl groups include, for example, thienyl, furanyl, thiazolyl, imidazolyl, (is)oxazolyl, pyridyl, pyrimidinyl, imidazolyl, (iso)quinolinyl, naphthyridinyl, benzimidazolyl, and benzoxazolyl.
Specific examples of heteroaryl groups are the following: 
wherein
L is nitrogen or xe2x80x94CR11;
T is xe2x80x94NR19, oxygen, or sulfur;
R11 and R11i are the same or different and are selected from hydrogen, halogen, hydroxy, C1-C6 alkyl, (C1-C6)alkoxy, amino, or mono- or di(C1-C6)alkylamino;
R12, R12i, and R13 are the same or different and are selected from hydrogen, halogen, (C1-C6)alkyl, (C1-C6)alkoxy, amino, mono- or di(C1-C6)alkylamino, hydroxy, or trifluoromethyl; and
R19 is hydrogen, lower alkyl having 1-6 carbon atoms.
The invention encompasses all possible tautomers and rotamers represented by Formula I.
By the term xe2x80x9chalogenxe2x80x9d in the present invention is meant fluorine, bromine, chlorine, and iodine.
Aryl and heteroaryl fused aminoalkyl-imidazoles of Formula I and their salts are suitable for the diagnosis and treatment of anxiety, Down Syndrome, sleep and seizure disorders, overdoses of benzodiazepine-type drugs, depression and cognitive disorders and for the enhancement of alertness, both in human and non-human animals and domestic pets, especially dogs and cats and farm animals such as sheep, swine and cattle. These interactions result in the pharmacological activites of these compounds.
The compounds of general Formula I may be administered orally, topically, parenterally, by inhalation or spray or rectally in dosage unit formulations containing conventional non-toxic pharmaceutically acceptable carriers, adjuvants and vehicles. The term parenteral as used herein includes subcutaneous injections, intravenous, intramuscular, intrasternal injection or infusion techniques. In addition, there is provided a pharmaceutical formulation comprising a compound of general Formula I and a pharmaceutically acceptable carrier. One or more compounds of general Formula I may be present in association with one or more non-toxic pharmaceutically acceptable carriers and/or diluents and/or adjuvants and if desired other active ingredients. The pharmaceutical compositions containing compounds of general Formula I may be in a form suitable for oral use, for example, as tablets, troches, lozenges, aqueous or oily suspensions, dispersible powders or granules, emulsion, hard or soft capsules, or syrups or elixirs.
Compositions intended for oral use may be prepared according to any method known to the art for the manufacture of pharmaceutical compositions and such compositions may contain one or more agents selected from the group consisting of sweetening agents, flavoring agents, coloring agents and preserving agents in order to provide pharmaceutically elegant and palatable preparations. Tablets contain the active ingredient in admixture with non-toxic pharmaceutically acceptable excipients which are suitable for the manufacture of tablets. These excipients may be for example, inert diluents, such as calcium carbonate, sodium carbonate, lactose, calcium phosphate or sodium phosphate; granulating and disintegrating agents, for example, corn starch, or alginic acid; binding agents, for example starch, gelatin or acacia, and lubricating agents, for example magnesium stearate, stearic acid or talc. The tablets may be uncoated or they may be coated by known techniques to delay disintegration and absorption in the gastrointestinal tract and thereby provide a sustained action over a longer period. For example, a time delay material such as glyceryl monosterate or glyceryl distearate may be employed.
Formulations for oral use may also be presented as hard gelatin capsules wherein the active ingredient is mixed with an inert solid diluent, for example, calcium carbonate, calcium phosphate or kaolin, or as soft gelatin capsules wherein the active ingredient is mixed with water or an oil medium, for example peanut oil, liquid paraffin or olive oil.
Aqueous suspensions contain the active materials in admixture with excipients suitable for the manufacture of aqueous suspensions. Such excipients are suspending agents, for example sodium carboxymethylcellulose, methylcellulose, hydropropylmethylcellulose, sodium alginate, polyvinylpyrrolidone, gum tragacanth and gum acacia; dispersing or wetting agents may be a naturally-occurring phosphatide, for example, lecithin, or condensation products of an alkylene oxide with fatty acids, for example polyoxyethylene stearate, or condensation products of ethylene oxide with long chain aliphatic alcohols, for example heptadecaethyleneoxycetanol, or condensation products of ethylene oxide with partial esters derived from fatty acids and a hexitol such as polyoxyethylene sorbitol monooleate, or condensation products of ethylene oxide with partial esters derived from fatty acids and hexitol anhydrides, for example polyethylene sorbitan monooleate. The aqueous suspensions may also contain one or more preservatives, for example ethyl, or n-propyl p-hydroxybenzoate, one or more coloring agents, one or more flavoring agents, and one or more sweetening agents, such as sucrose or saccharin.
Oily suspensions may be formulated by suspending the active ingredients in a vegetable oil, for example arachis oil, olive oil, sesame oil or coconut oil, or in a mineral oil such as liquid paraffin. The oily suspensions may contain a thickening agent, for example beeswax, hard paraffin or cetyl alcohol. Sweetening agents such as those set forth above, and flavoring agents may be added to provide palatable oral preparations. These compositions may be preserved by the addition of an anti-oxidant such as ascorbic acid.
Dispersible powders and granules suitable for preparation of an aqueous suspension by the addition of water provide the active ingredient in admixture with a dispersing or wetting agent, suspending agent and one or more preservatives. Suitable dispersing or wetting agents and suspending agents are exemplified by those already mentioned above. Additional excipients, for example sweetening, flavoring and coloring agents, may also be present.
Pharmaceutical compositions of the invention may also be in the form of oil-in-water emulsions. The oily phase may be a vegetable oil, for example olive oil or arachis oil, or a mineral oil, for example liquid paraffin or mixtures of these. Suitable emulsifying agents may be naturally-occurring gums, for example gum acacia or gum tragacanth, naturally-occurring phosphatides, for example soy bean, lecithin, and esters or partial esters derived from fatty acids and hexitol, anhydrides, for example sorbitan monoleate, and condensation products of the said partial esters with ethylene oxide, for example polyoxyethylene sorbitan monoleate. The emulsions may also contain sweetening and flavoring agents.
Syrups and elixirs may be formulated with sweetening agents, for example glycerol, propylene glycol, sorbitol or sucrose. Such formulations may also contain a demulcent, a preservative and flavoring and coloring agents. The pharmaceutical compositions may be in the form of a sterile injectable aqueous or oleaginous suspension. This suspension may be formulated according to the known art using those suitable dispersing or wetting agents and suspending agents which have been mentioned above. The sterile injectable preparation may also be sterile injectable solution or suspension in a non-toxic parentally acceptable diluent or solvent, for example as a solution in 1,3-butanediol. Among the acceptable vehicles and solvents that may be employed are water, Ringer""s solution and isotonic sodium chloride solution. In addition, sterile, fixed oils are conventionally employed as a solvent or suspending medium. For this purpose any bland fixed oil may be employed including synthetic mono-or diglycerides. In addition, fatty acids such as oleic acid find use in the preparation of injectables.
The compounds of general Formula I may also be administered in the form of suppositories for rectal administration of the drug. These compositions can be prepared by mixing the drug with a suitable non-irritating excipient which is solid at ordinary temperatures but liquid at the rectal temperature and will therefore melt in the rectum to release the drug. Such materials are cocoa butter and polyethylene glycols.
Compounds of general Formula I may be administered parenterally in a sterile medium. The drug, depending on the vehicle and concentration used, can either be suspended or dissolved in the vehicle. Advantageously, adjuvants such as local anesthetics, preservatives and buffering agents can be dissolved in the vehicle.
Dosage levels of the order of from about 0.1 mg to about 140 mg per kilogram of body weight per day are useful in the treatment of the above-indicated conditions (about 0.5 mg to about 7 g per patient per day). The amount of active ingredient that may be combined with the carrier materials to produce a single dosage form will vary depending upon the host treated and the particular mode of administration. Dosage unit forms will generally contain between from about 1 mg to about 500 mg of an active ingredient.
Frequency of dosage may also vary depending on the compound used and the particular disease treated. However, for treatment of most disorders, a dosage regimen of 4 times daily or less is preferred. For the treatment of anxiety or depression a dosage regimen of 1 or 2 times daily is particularly preferred. For the treatment of sleep disorders a single dose that rapidly reaches effective concentrations is desirable.
It will be understood, however, that the specific dose level for any particular patient will depend upon a variety of factors including the activity of the specific compound employed, the age, body weight, general health, sex, diet, time of administration, route of administration, and rate of excretion, drug combination and the severity of the particular disease undergoing therapy.
Preferred compounds of the invention will have certain pharmacological properties. Such properties include, but are not limited to oral bioavailability, low toxicity, low serum protein binding and desirable in vitro and in vivo half-lifes. Penetration of the blood brain barrier for compounds used to treat CNS disorders is necessary, while low brain levels of compounds used to treat periphereal disorders are often preferred.
Assays may be used to predict these desirable pharmacological properties. Assays used to predict bioavailability include transport across human intestinal cell monolayers, including Caco-2 cell monolayers. Toxicity to cultured hepatocyctes may be used to predict compound toxicity. Penetration of the blood brain barrier of a compound in humans may be predicted from the brain levels of the compound in laboratory animals given the compound intravenously. Serum protein binding may be predicted from albumin binding assays. Such assays are described in a review by Oravcovxc3xa1, et al. (Journal of Chromatography B (1996) volume 677, pages 1-27).
Compound half-life is inversely proportional to the frequency of dosage of a compound. In vitro half-lifes of compounds may be predicted from assays of microsomal half-life as described by Kuhnz and Gieschen (Drug Metabolism and Disposition, (1998) volume 26, pages 1120-1127).
The present invention also pertains to packaged pharmaceutical compositions for treating disorders responsive to GABAA receptor modulation, e.g., treatment of cognitive deficits, anxiety or depression by GABAA receptor modulation. The packaged pharmaceutical compositions include a container holding a therapeutically effective amount of at least one GABAA receptor modulator as described supra and instructions (e.g., labeling) indicating the contained GABAA receptor ligand is to be used for treating a disorder responsive to GABAA receptor modulation in the patient.
The present invention also pertains to methods for altering the signal-tranducing activity of GABAA receptors, said method comprising exposing cells expressing such receptor to an effective amount of a compound of the invention.
A method of inhibiting the binding of a benzodiazepine compound to the benzodiazepine site of the GABAA receptor, comprising contacting a compound of Formula I with cells expressing such a receptor in the presence of a the benzodiazepine compound, wherein the compound is present at a concentration sufficient to inhibit benzodiazepine compound binding to cells expressing a cloned human GABAA receptor in vitro is provided by a separate aspect of the invention.
In a separate aspect, the invention provides a method of potentiating the actions of other CNS active compounds, which comprises administering an effective amount of a compound of the invention in combination with another CNS active compound. Such CNS active compounds include, but are not limited to the following: for anxiety, serotonin receptor (e.g. 5-HT1A) agonists and antagonists; for anxiety and depression, neurokinin receptor antagonists or corticotropin releasing factor receptor (CRF1) antagonists; for sleep disorders, melatonin receptor agonists; and for neurodegenerative disorders, such as Alzheimer""s dementia, nicotinic agonists, muscarinic agents, acetylcholinesterase inhibitors and dopamine receptor agonists. Particularly the invention provides a method of potentiating the antidepressant activity of selective serotonin reuptake inhibitors (SSRIs) by administering an effective amount of a GABA agonist compound of the invention in combination with an SSRI.
Combination administration can be carried out in an analogous fashion to that disclosed in Da-Rocha, et al., J. Psychopharmacology (1997) 11(3) 211-218; Smith, et al., Am. J. Psychiatry (1998) 155(10) 1339-45; and Le, et al., Alcohol and Alcoholism (1996) 31 Suppl. 127-132. Also see, the discussion of the use of the GABAA receptor ligand 3-(5-methylisoxazol-3-yl)-6-(1-methyl-1,2,3-triazol-4-yl)methyloxy-1,2,4-triazolo [3,4-a]phthalzine in combination with nicotinic agonists, muscarinic agonists, and acetylcholinesterase inhibitors, in PCT International publications Nos. WO 99/47142, WO 99/47171, and WO 99/47131, respectively. Also see in this regard PCT International publication No. WO 99/37303 for its discussion of the use of a class of GABAA receptor ligands, 1,2,4-triazolo[4,3-b]pyridazines, in combination with SSRIs.
The disclosures of all articles and references mentioned in in this application, including patents, are incorporated herein by reference.